Project Summary/Abstract Multimorbidity, defined as the co-occurrence of two or more chronic conditions, is common and costly, but currently there are no recommended treatments to delay its progression. High blood pressure (BP) is both the single most common chronic condition among US adults and a risk factor for many additional chronic conditions. Treatment of hypertension has the potential to delay the progression of multimorbidity by preventing stroke, coronary heart disease (CHD), heart failure (HF), chronic kidney disease (CKD), peripheral vascular disease, and atrial fibrillation. Although hypertension treatments are effective and inexpensive, a large percentage of older adults taking antihypertensive medications have uncontrolled BP. Older adults describe their health goals in terms of reducing the burden of chronic disease, maintaining functional independence, and avoiding nursing home placement, in contrast to achieving disease-specific treatment goals. Because prior hypertension clinical trials have conceptualized study endpoints as discrete outcomes and not collected outcomes that signal functional decline including nursing home placement, they may underestimate the benefit of BP control in the real-world context where people experience co-occurring chronic conditions. The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) provides a unique and cost efficient opportunity to study BP and the progression of multimorbidity. ALLHAT is a large simple trial of 42,418 high-risk hypertensive patients between 1994 and 1998 and was designed to determine the differential effect of antihypertensive medications from three drug classes. ALLHAT is ideal for studying multimorbidity given its broad inclusion criteria, and large number of participants > 65 years, women, and African Americans. We will use ALLHAT data from approximately 20,000 participants ? 65 years with Medicare fee-for-service coverage and obtain Medicare inpatient (Part A), outpatient (Part B), PAC, and long-term care claims to address the following specific aims: 1) to determine the impact of sustained BP control on the delay of multimorbidity progression, 2) to evaluate the associations between sustained BP control and the development of specific high cost/high disability chronic condition clusters, 3) to compare the effect of antihypertensive medication classes on multimorbidity progression and the development of specific high cost/high disability chronic condition clusters and 4) to determine the long-term impact of delayed multimorbidity progression on inpatient and PAC utilization in inpatient rehabilitation facilities, skilled nursing facilities, and home health services and long-term care in nursing homes. The current study will provide evidence to reframe the discussion about BP control from a ?treating the numbers? perspective to more patient-centered perspective. Ultimately, demonstrating the value of sustaining controlled BP on outcomes that matter to older adults including reducing the burden of chronic disease, maintaining functional independence, and avoiding nursing home placement, will provide motivation to both physicians and patients to work to achieve better BP control.